package com.fulin.sycnLife;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;
import java.util.concurrent.RecursiveTask;

/**
 * jdk的fork/join框架实现实例
 * 
 * 将一个大任务拆分成小任务,然后执行
 * 
 * @author fulin16
 *
 */
public class CountTask extends RecursiveTask<Integer>{

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private static final int THRESHOLD = 2;//阈值
	private int start;
	private int end;
	public CountTask(int start,int end){
		this.start = start;
		this.end = end;
	}
	
	@Override
	protected Integer compute() {
		int sum = 0;
		boolean canCompute = (end - start) <= THRESHOLD;
		if(canCompute){
			for(int i = start;i <= end; i++){
				sum += i;
			}
		}else{
			//如果任务大于阀值,就分裂成两个子任务计算
			int middle = (start + end ) / 2;
			CountTask leftTask = new CountTask(start,middle);
			CountTask rightTask = new CountTask(middle + 1,end);
			//执行子任务
			leftTask.fork();
			rightTask.fork();
			//等待子任务执行完成，并得到其结果
			int leftResult = leftTask.join();
			int rightResult = rightTask.join();
			//合并子任务
			sum = leftResult + rightResult;
		}
		return sum;
	}
	
	public static void main(String[] args) {
		ForkJoinPool forkJoinPool = new ForkJoinPool();
		//生成一个计算任务，负责计算1+2+3+4
		CountTask task = new CountTask(1,4);
		//执行一个任务
		Future<Integer> result = forkJoinPool.submit(task);
		try{
			System.out.println(result.get());
		}catch(InterruptedException e){
			
		}catch(ExecutionException e){}
	}
}
